Heat exchanger, particularly for cooling fresh cracked and/or synthesis gases

ABSTRACT

A heat exchanger particularly for cooling fresh cracked and/or synthesis gases produced through high pressure and high temperature having a casing with an inlet and outlet for gases. Straight casing pipes closed at their lower ends are located in the casing with centrally located immersion tubes of smaller diameter than the casing pipes for the supply of coolants in the casing pipes. A plurality of pipes forming rows of pipes spaced from one another and a plurality of rows of pipes spaced parallel next to each other are gathered into a nest of pipes. Longitudinal fins connect the casing pipes forming rows of pipes and the casing pipes standing opposite each other of adjacent rows of pipes. The casing pipes of the individual rows of pipes are of such length that their ends form parallel rows to each other aligned perpendicular to the longitudinal axis of the casing pipes. The rows going out from both outer rows toward the center of the nest of pipes gradually rise from pipe row to pipe row. The inlet and outlet side of the nest of pipes are covered with a conical gas inlet and gas outlet head and the length of the casing pipes is such, that a row of pipes in the area of said inlet and outlet heads increase gradually according to the conicity of the heads.

United States Patent Clausset al.'

1541 HEAT EXCHANGER, PARTICULARLY FOR COOLING FRESH CRACKEDAND/ORSYNTHESIS GASES Inventors: Gerhard vClauss; Helrnut Herrmann, bothof Kassel, Germany A Assignee: Schmidtsche Heissdampf-Gmbl-I,

Kassel-Bettenhausen, Germany Filed: Feb. 26, 1970 Appl. No.: 14,498

, Foreign Application Priority March 5, 1969 Germany ..P l9 11 195.6

US. Cl ..165/ 136, 122/305, 23/277 R,"

References Cited UNITED STATES PATENTS 8/1902 Vicente ..l22/305 '6/19222/1967 7/1969 Palchik ..165/ 142 FOREIGN PATENTS OR APPLICATIONS 3/1950Great Britain.....'., ..165/183 Werner ..l65/l42 f Vollhardt ..165/140Primary Examiner-Albert W. Davis, Jr. Att0rneyWenderoth, Lind & PonackABSTRACT A heat exchanger particularly for cooling fresh I crackedand/or synthesis gases produced through high pressure and hightemperature having a casing with an inlet and outlet for gases.Straightcasing pipes closed at their lower ends are located in thecasing with centrally located immersion tubes of smaller diameter thanthe casing pipes for the supply of coolants in the casing pipes. Aplurality of pipes forming rows of pipes spaced from one another and aplurality of rows of pipes spaced parallel next to each other aregathered into a nest of pipes. Longitudinal fins connect the casingpipes forming rows of pipes and the casing pipes standing opposite eachother of adjacent rows of pipes. The casing pipes of theindividual rowsof pipes are of such length that their ends form parallel rows to eachother aligned perpendicular to the longitudinal axis of the casingpipes. The rows going out from both outer'rows toward the center of thenest of pipes gradually rise from pipe row to pipe row. The inlet andoutlet side of the nest of pipes are covered with a conical gas inletand gas outlet head and the length of the casing pipes is such, that arow of pipes in the area of said inlet and outlet heads increasegradually according to the conicity of the heads.

7 Clair 1s, 3 Drawing Figures 15] 3,682,241 45] Aug. 8, 1972 UnitedStates Patent Clauss et a].

PATENTEU M19 8 I972 SHEET 1 [1F 3 FIG.I

INVENTORS GERHARD CLAUSS HELMUT HERRMANN MW ZMA 4c ATTORNEYS PATENTEDAUG8 I972 SHEET 2 OF 3 INVENTOIB GERHARD CLAUSS HELMUT HERRMANN v PATENTEDAUG 8 I972 SHEET 3 OF 3 m NS ES m L C D R A H R E G HELMUT HERR MANNZQQWZZ, ,4.d /g

1 HEAT EXCHANGER, PARTICULARLY FOR COOLING FRESH CRACKED AND/ORSYNTHESIS with centrally located immersion tubes of smaller diameter forthe supply of coolants, of which a majority form rows of pipes spacedfrom one another and several rows of pipes spaced parallel next to oneanother gathered into a nest of pipes.

In order to produce olefins, particularly ethylene, from gaseous orevaporated liquid hydrocarbons, they are subjected to a thermal crackingin a cracking furnace. The cracked gas a mixture of gases which is veryreactive and has to be cooled to prevent regeneration.

This requires especially-developed heat exchangers. Such heat exchangersshould not only be built to handle high pressure and high temperature,but should also be able to counteract in the heat exchanger as much aspossible the regenerating tendency of the cracked gases which means thatthe undesired precipitation of coke and condenstaion precipitates orother cracked products, in order to avoid as much as possible thesoiling of the heating surface which causes an undesirable reduction ofthe cooling efiect and a smaller production of the desired end productdue to said regeneration. With such heat exchangers, attention has alsoto be given to the cracked gas which flows into the heat exchangers orthe process gas obtained from the gasification of the pressure oil sothat it does not waste any time entering the cooling, because the timewhich the gas needs from the moment it enters the heat exchanger untilits impact upon the cooling surface, has been proven to be related tothe amount of tion of the cracked gas.

Besides, the heat exchanger is supposed to allow a secure control ofhigh thermal stress of the cooling surfaces and it should permit anefficient utilization of the perceptible heat resulting from the gasesof the cooling medium through a boiler for the production of energy. I

A number of heat exchangers are known which generally only fulfillpartially the above mentioned requirements.

Fire tube heat exchangers are composed of a casing surrounding a waterspace with tube plates on both ends and the fire tubes which passthrough the water space. Such heat exchangers are not very suitable forthe cooling of cracked gases, since the tube-plates as well as thecasing, due to the cooling wall temperatures which have to bemaintained, have to resist a very high pressure of .the boiling coolantof approximately 80-200 gauge pressure measured in atmospheres andtherefore requires a casing with strong walls as well as strong tubeplates. Therefore, these heat exchangers are very expensive from thepoint of view of construction and material. Besides, due particularly toa high accumulation of material, at the side of the entry of the heatinggas they are very susceptible to the phenomenon of heat accumulation,caused by the high heat supply from the heating gases which leads to theburning of material, particularly of the fire tubes. Such heatexchangers require special precautions, so that the heating agentimmediately after entering the gas entry side of the heat exchanger, canwithout delay or turbulence be grought to act upon the cooling surfacesand can be led to the fire tubes. It is an'object of the invention toavoid such disadvantages.

' There are also known heat exchangers whereby the cooling surfaces areformed by water pipes which are arranged in a casing passed through byheating gases, the casingcan also enclose water pipes provided withlongitudinal fins. This kind of heat exchanger is not very suitable forcooling cracked gases, because in the entry area the feed pipes whichare set more or less perpendic'ular to the direction of the flow of theheated agent thus reducing its free flow section offers resistance tothe cooling agent, which prevents a turbulence free entry of the heatedagent into the area of the cooling surface, which unavoidably leads tosuch delays at the entry side of the heat exchanger, that undesirableregeneration phenomenon takes place. As compared to this known device,the present invention has for an object a construction wherein thecasing pipes forming regenerarows of pipes as well as the casing pipesstanding opposite each other in adjacent rows of pipes are connectedwith each other through longitudinal fins and the casing pipes of theindividual pipe rows are of such length, that their ends form parallelrows to each other aligned perpendicular to the longitudinal axis of thecasing pipes, and these rows starting from both outer pipe rows towardthe center of .the nest of pipes rise gradually from pipe row to piperow.

A further object is to provide a heat exchanger built according to thisinvention which does not have at the inflow side any built-in objectswhich interfere with the flow and which could cause turbulence of theheating gases before they flow into the pipe alleys and thus couldproduce an undesired increase of waiting time, so that the' medium beingsupplied for cooling can flow without hindrance into the pipe alleys,whereby the waiting period in' the inflow side of the heat exchanger isreduced to a harmless minimum.

A still further object is to provide a construction wherein a harmfullocalization of heat due to accumulation of material cannot occur,because there do not exist such masses of material. In addition such aheat exchanger due to its special cooling surfaces which consist of socalled field pipes, from the point of view of the cooling media andwithout having an excessive expenditure for material can resist even thehighest pressures.

A further object is to achieve a particularly turbulent free inflow ofthe cracked gas onto the cooling area, that is to say into the pipealleys, and in order to secure a resistance free outflow of the crackedgas after its cooling, the in and outflow ends of the pipe nest areprovided correspondingly with a conical gas inlet and outlet head andthe length of the casing pipes of the individual pipe rows is such, thatthe pipe rows in the area of the conical part of the gas inlet and/orgas outlet head rise gradually according to their conicity.

For the feeding of the cooling agent and the outlet of the mixture ofsteam the immersion pipes and the casing pipes of the nest of pipes areconnected on their upper ends through feeding and runout lines with twodistributors located at two opposite sides of the gas butlet head andwith the collectors located on the remaining free sides of the gasoutlet head. This allows an advantageously compact and uniformconstruction.

A further object in order to prevent heat losses of the heat exchangerthrough radiation, to the outside arid in" order to guarantee a freeexpansion of the pipe nest,

' the distributors and accumulators connected with the pipe nest throughfeeding and outlet lines are set firmly inla header linedrefractorymaterial, which is set on a casing piece lined with thermalinsulation which surrounds the center. section of the pipe nest leavinga clearance in between, said casing piece being connected in turn with afoot piece equally lined with thermal insulation where the head-of thegas entrance is located intowhich the lower ends of the casing pipesproject.

Since due to the localization of the upper ends of the casing pipes theycan expand freely into the gas entrance head according to the thermalstress, the lower 'endsof the casing pipes of the nest of tubes aretherefore not connected firmly and tightly with the gas en- Y edge, saidplate lying at a distance abovethe footpiece and parallel to the upperfoot piece surface, its greatest diameter being smaller than the insidediameter of the lining of the casing and its free edge being sunk into acorresponding recess in the foot piece surface which 2 serves as a sandseal.

A different advantageous construction of the sealing between the freeedge of said plate consists in setting into the recess of the footsurface area flexible sealings, onto which the free edge of the sidewall of the plate rests.

' heat exchange elements 5 in the so called field pipe 4, It isadvantageous if theplate together with the lower pipes with flowfavoring casing heads made of a heatresisting material.

With the above and other objects in view which will manner. The coolingagent is fed through the feed pipes 6 which discharge into the upper endof the immersion pipes 3. The steam mixture fonned in theannulus 4through heating of easing pipes l is led off through the outlet pipe 7connected onto'the upper end of easing pipe 1. 3

A multiplicity'of casing pipes 1, that 'is to say heat exchange elements5,standin'g spaced from each other arecombined into a pipe row-,8.Several of these rows of pipes'8 are arranged spaced from each other andparallel to one another,and thus form the nest of pipes 2. Casing pipesl which form rows of pipes 8, that is to space between casing pipes 1.This creates a uniform, cooling'surface impermeable to gases with alleys10 between the heat exchange elements 5 for the circulation of thethermal agent.

It is understood that the longitudinal fins 9 within the nest of pipes 2do not need to be welded to each other, they only serve to space andbrace the casing pipes among each other. In this case no tight alleys 10against each other are formed, which actually is not necessary either.These alleys 10, the same as the tight alleys, can be easily cleanedwith high pressure jet devices.

At the lower entrance and upper exit end of the nest of pipes 2 there isa conical gas entrance head 11, and/or a gas entrance head 12.-'Ihecasing pipes 1 of the individual row of pipes 8 which project with theirends into the conical part of the gas entrance and/or gas outlet head 11and 12, are of such length that their ends perpendicular to thelongitudinal axis of the casing-pipes l are aligned so that they formparallel rows to each other, and these rows of the nest of pipes 2increase gradually from one row of pipes 8 to the next row of pipes8.The length of the casing pipes l of the individual row of pipes 8 ischosen in such a manner, that the row of pipes 8 in the conicalarea ofthe gas entrance and/or gas outlet head 11 and 12 increase graduallycorresponding to such conicity.

become apparent from the detailed description below,

. a preferred form of the invention is shown in the drawings in which:

. FIG. 1 shows the heat exchanger in a longitudinalcenter section on theline l--l of FIG. 2,

- FIG. 2 shows the heat exchanger in a cross section on the line 2-2 ofFIG. .1, and

FIG. 3 shows the heat exchanger in a longitudinal.

. pipes 1 and immersion pipes 3 are gathered to form The immersion pipes3 of the heat exchange elements 5 are connected through the feed pipes 6with are set horizontally next to the gas outlet head 12 on its freeside. The steam mixture flowing to accumulators 14 out of the heatexchange elements 5 is led to a steam drum (not shown) for evaporation,from which the steam is taken to supply steam consumers.

In order to avoid heat losses through radiation to the outside and allowa free expansion of the nest of pipes 2, the in and outflow conduits 6and 7 together with the distributors 13 and accumulators 14 connectedwith the nestof pipes 2 are set firmly into a head piece lined withrefractory material, said headpiece being set on the central part of thenest of pipes 2 in a casing 16 sursegment of the nest of pipes 2 incasing 16 and the footpart 17 can be sealed gastight, there is set onthe lower end of the nest of pipes and connected in a gastight mannerwith the latter a plate 21 at a certain distance above foot part 17 andparallel to the upper foot plane 19, said plate 21 has around itslateral edge a side wall 20 and its largest diameter is smaller than theinside diameter of the casings lining 16. The free edge 22 of side wall20 immerses into a recess 23 extending all around the foot plane 19 ofthe foot part 17 filled with sand to form a sand seal. In order toimprove the seal a flexible seal 24 can be set into recesses 23 ontowhich rests the free edge 22 of side wall 20. In order to obtain,particularly in the lower area of the nest of pipes 2 a good thermalinsulation a casing 25 of thermal insulating material is set onto plate21, which encloses the nest of pipes 2.

So as to protect the lower ends of casing pipes 1 from burning orscaling and in order to achieve an effective distribution of theinflowing gas jet, there are set onto the lower ends of the casing pipes1 casing hats 26 formed favorably to the flow and made of heat-resistingmaterial.

We claim:

1. Heat exchanger particularly for cooling fresh cracked and/orsynthesis gases produced through high pressure and high temperaturecomprising a casing having an inlet and outlet for gases, straightcasing pipes closed at their lower ends in said casing, immersion tubesof smaller diameter than said casing pipes for a supply of coolantscentrally located in said casing pipes, a plurality of said pipesforming rows of pipes spaced from one another, said rows of said pipesbeing parallel and forming a nest of pipes, longitudinal fins (9)connecting said casing pipes (l) forming rows of pipes (8), said casingpipes (1) standing opposite each other in adjacent rows of said pipes,said casing pipes (l) of the individual rows of pipes (8) being of suchlength that their ends form parallel rows to each other alignedperpendicular to the longitudinal axes of said casing pipes, and saidrows extending from both outer rows (8) toward the center of said nestof pipes (2) rising stepwise from pipe row to pipe row said nest ofpipes 2 has an inlet and outlet side covered with a conicalgas inlet andgas outlet head (11 and 12) and the length of said casing pipes (l)forming a row of pipes (8) in the area of said inlet and outlet headsincrease stepwise according to the conicity ofsaid heads.

2. Heat exchanger according to claim 1 wherein said immersion tubes andsaid casing pipes are connected at their upper ends by feeding andoutlet lines with two distributors located at two opposite sides-of saidgas outlethead and with accumulators 14 located on th remaining sides ofsaid gas outlet head.

3. Heat exchanger according to claim 2 wherein said distributors andsaid accumulators are connected with said nest of pipes through saidfeeding and outlet lines set firmly in head li ed casing piece lined wrti'it erm ins atron on w lch sar header is mounted, said casing piecesurrounding the center section of said nest of pipes and being spacedtherefrom, a foot piece having a recess is lined with thermal insulationto which said casing piece is connected where the inlet of said easinginto which the lower ends of said casing pipes project, is located.

4. Heat exchanger according to claim 2, wherein a plate is connected onthe lower end of said nest of pipes in a gas tight manner having a sidewall on the periphery thereof, said plate lying at a distance above saidfoot piece parallel to the upper foot piece surface having its greatestdiameter smaller than the inside diameter of said casing and said sidewall having its free edge immersed into said recess which serves as asand seal.

5. Heat exchanger according to claim 4, wherein flexible sealings areset into said recess on which the free edge of said side wall (20)rests.

6. Heat exchanger according to claim 5 wherein a casing ofthermalinsulating material is installed on said plate surrounding thelower part of said nest of pipes.

7. Heat exchanger according to claim 4 wherein the free lower ends ofsaid casing pipes are provided with flow favoring casing heads made ofheat resisting material.

'th re ractory m terial,

1. Heat exchanger particularly for cooling fresh cracked and/orsynthesis gases produced through high pressure and high temperaturecomprising a casing having an inlet and outlet for gases, straightcasing pipes closed at their lower ends in said casing, immersion tubesof smaller diameter than said casing pipes for a supply of coolantscentrally located in said casing pipes, a plurality of said pipesforming rows of pipes spaced from one another, said rows of said pipesbeing parallel and forming a nest of pipes, longitudinal fins (9)connecting said casing pipes (1) forming rows of pipes (8), said casingpipes (1) standing opposite each other in adjacent rows of said pipes,said casing pipes (1) of the individual rows of pipes (8) being of suchlength that their ends form parallel rows to each other alignedperpendicular to the longitudinal axes of said casing pipes, and saidrows extending from both outer rows (8) toward the center of said nestof pipes (2) rising stepwise from pipe row to pipe row said nest ofpipes 2 has an inlet and outlet side covered with a conical gas inletand gas outlet head (11 and 12) and the length of said casing pipes (1)forming a row of pipes (8) in the area of said inlet and outlet headsincrease stepwise according to the conicity of said heads.
 2. Heatexchanger according to claim 1 wherein said immersion tubes and saidcasing pipes are connected at their upper ends by feeding and outletlines with two distributors located at two opposite sides of said gasoutlet head and with accumulators 14 located on the remaining sides ofsaid gas outlet head.
 3. Heat exchanger according to claim 2 whereinsaid distributors and said accumulators are connected with said nest ofpipes through said feeding and outlet lines set firmly in a header linedwith refractory material, a casing piece lined with thermal insulationon which said header is mounted, said casing piece surrounding thecenter section of said nest of pipes and being spaced therefrom, a footpiece having a recess is lined with thermal insulation to which saidcasing piece is connected where the inlet of said casing into which thelower ends of said casing pipes project, is located.
 4. Heat exchangeraccording to claim 2, wherein a plate is connected on the lower end ofsaid nest of pipes in a gas tight manner having a side wall on theperiphery thereof, said plate lying at a distance above said foot pieceparallel to the upper foot piece surface having its greatest diametersmaller than the inside diameter of said casing and said side wallhaving its free edge immersed into said recess which serves as a sandseal.
 5. Heat exchanger according to claim 4, wherein flexible sealingsare set into said recess on which the free edge of said side wall (20)rests.
 6. Heat exchanger according to claim 5 wherein a casing ofthermal insulating material is installed on said plate surrounding thelower part of sAid nest of pipes.
 7. Heat exchanger according to claim 4wherein the free lower ends of said casing pipes are provided with flowfavoring casing heads made of heat resisting material.